Parent.prototype.sex = {a: 1}
Parent.prototype.a = {n: 2}
function Parent() {
  this.name = 'Tom'
  this.like = ['running', 'swimming']
}

Child.prototype = Object.create(Parent.prototype)  // new Parent()
                  // {a: {n: 1}}.__proto__ = Parent.prototype

Child.prototype.constructor = Child
Child.prototype.a = {n: 1}
function Child() {
  Parent.call(this)
  this.age = 18
}

let c = new Child()

console.log(c.a.n = 100);


